diff --git a/map.js b/map.js
index 6603920c..9d2e47dc 100644
--- a/map.js
+++ b/map.js
@@ -13,6 +13,10 @@ function initMap() {
         "map": null,
         // The selected (or initial) municipality:
         "activeMunicipality": "Hoorn",
+        // The selected (or initial) period:
+        "period": "14d",
+        // Indicates the status of the period filter:
+        "isHistoryActive": false,
         // The zoom level when starting the app:
         "initialZoomLevel": 16,
         // The marker objects of the municipalities:
@@ -25,8 +29,6 @@ function initMap() {
         "publicationsArray": [],
         // Backup of the recent publications, because loading them again is slow:
         "publicationsArrayBackup": [],
-        // Indicates the status of the time filter:
-        "isHistoryActive": false,
         // Indicates if all parts are loaded:
         "isFullyLoaded": false,
         // Order of different license markers, newest on top. Set to some high number:
@@ -54,6 +56,15 @@ function initMap() {
                 console.log("Adjusted municipality from URL: " + municipalityParam);
             }
             center = Object.assign({}, municipalities[appState.activeMunicipality].center);
+            if (periodParam) {
+                const period = periods.find(function (p) {
+                     return p.key === periodParam;
+                });
+                if (period !== undefined) {
+                    appState.period = period.key;
+                    console.log("Adjusted period " + period.key + " from URL");
+                }
+            }
             if (zoomParam && centerParam) {
                 zoomParam = parseFloat(zoomParam);
                 if (zoomParam > 14 && zoomParam < 20) {
@@ -691,20 +702,14 @@ function initMap() {
 
         const result = {
             "elm": document.getElementById("idCbxPeriod"),
-            "period": "14d",
-            "periodToShow": "14d",
-            "isHistory": false
+            "period": appState.period,
+            "isHistory": isHistoricalPeriod(appState.period)
         };
-        if (result.elm === null) {
-            return result;  // Default when loading
-        }
         // If this is an historical period, default to 'all':
-        result.period = result.elm.value;
-        if (isHistoricalPeriod(result.elm.value)) {
+        if (result.isHistory) {
             result.periodToShow = "all";
-            result.isHistory = true;
         } else {
-            result.periodToShow = result.elm.value;
+            result.periodToShow = appState.period;
         }
         return result;
     }
@@ -811,6 +816,7 @@ function initMap() {
                 markerObject.marker.setVisible(isMarkerVisible(markerObject.age, periodFilter.periodToShow));
             });
         }
+        updateUrl(appState.map.getZoom(), appState.map.getCenter());
     }
 
     /*